The invention relates to hydrocarbon production from wells drilled in a subterranean formation. Hydrocarbon is obtained from a subterranean formation by drilling a wellbore that penetrates the hydrocarbon-bearing formation. It is desirable to maximize both the rate of flow and the overall amount of flow of hydrocarbon from the subterranean formation to the surface.
The rate of hydrocarbon flow and the overall amount of hydrocarbon flow declines when the bottom hole flowing pressure falls below the dew point. When this occurs, a liquid aqueous phase accumulates near the well. This condensate accumulation, sometimes called condensate blocking, reduces the hydrocarbon relative permeability and thus the well's hydrocarbon productivity. The productivity loss associated with condensate buildup can be substantial. In some cases, well productivities can decline by a factor of 2 to 4 as a result of condensate accumulation.
The rate of hydrocarbon flow and the overall amount of hydrocarbon flow can be impacted when well treatment fluids such as fracturing fluids, gravel pack fluids, and aqueous acidizing fluids are injected into the formation. Well treatment fluids sometimes decrease hydrocarbon's relative permeability through the formation compared to other fluids in the reservoir because of the limited reservoir pressure and capillary forces tightly holding the treatment fluids in the pore spaces previously occupied by hydrocarbon. The pockets of treatment fluid, which are interlocked with hydrocarbon, are hard to remove from the formation without some kind of stimulation treatment.
Another way that the rate of hydrocarbon flow and the overall amount of hydrocarbon flow is reduced is by fines production or sand migration in the formation or by precipitation. The high velocity in the porous medium near the wellbore is sometimes sufficient to mobilize fines that can then plug channels in the formation. More often, formation sand and fines often become unstable and migrate as a result of water movement through the formation. Fines are most likely to move when the phase they wet is mobile, and since most formation fines are water-wet, the presence of a mobile water phase can cause fines migration and subsequent formation damage. It is desirable to minimize fines migration, since fines block flow paths, choking the potential production of the well, as well as causing damage to downhole and surface equipment, such as screens, pumps, flow lines, storage facilities, etc.
The problem of fines production is especially a problem in unconsolidated subterranean zones. Hydrocarbon wells are often located in subterranean zones that contain unconsolidated particulates that may migrate within the subterranean formation with the oil, gas, water, and/or other fluids produced by the wells. The presence of particulates, such as formation sand, in produced fluids is disadvantageous and undesirable in that the particulates may abrade pumping and other producing equipment and reduce the fluid production capabilities of the producing zones. Unconsolidated subterranean zones include those that contain loose particulates and those wherein the bonded particulates have insufficient bond strength to withstand the forces produced by the production of fluids through the zones.
One method of controlling particulates in unconsolidated formations involves placing a filtration bed containing sand or “gravel” near the well bore in order to present a physical barrier to the transport of unconsolidated formation fines with the production of hydrocarbons. Typically, such gravel packing operations involve the pumping and placement of a quantity of a desired particulate into the unconsolidated formation in an area adjacent to a well bore.
One common type of gravel packing operation involves placing a gravel pack screen in the well bore and packing the surrounding annulus between the screen and the well bore with gravel of a specific size designed to prevent the passage of formation sand. The gravel pack screen is generally a filter assembly used to retain the gravel placed during gravel pack operation. A wide range of sizes and screen configurations are available to suit the characteristics of the gravel pack sand used. Similarly, a wide range of sizes of gravel is available to suit the characteristics of the unconsolidated or poorly consolidated particulates in the subterranean formation. The resulting structure presents a barrier to migrating sand from the formation while still permitting fluid flow.
When installing the gravel pack, the gravel is carried to the formation in the form of a slurry by mixing the gravel with a viscose transport fluid. Once the gravel is placed in the well bore, the viscosity of the transport fluid is reduced, and it is returned to the surface. Some gravel packing operations, commonly known as “high-rate water packing” operations, the transport fluid viscosity is somewhat lowered and yet the gravel remains in suspension because the treatment occurs at a substantially higher velocity.
Gravel packs, inter alia act to stabilize the formation while causing minimal impairment to well productivity. The gavel, inter alia, acts to prevent the particulates from occluding the screen or migrating with the produced fluids. The screen, inter alia, acts to prevent the gravel from entering the production tubing. However, such gavel packs may be time consuming and expensive to install.
Another method used to control particulates in unconsolidated formations involves consolidating a subterranean producing zone into hard, permeable masses. Consolidation of a subterranean formation zone often involves applying a resin followed by a spacer fluid and then a catalyst. Such resin application may be problematic when, for example, an insufficient amount of spacer fluid is used between the application of the resin and the application of the external catalyst. The resin may come into contact with the external catalyst in the well bore itself rather than in the unconsolidated subterranean producing zone. When resin is contacted with an external catalyst, an exothermic reaction occurs that may result in rapid polymerization, potentially damaging the formation by plugging the pore channels, halting pumping when the well bore is plugged with solid material, or resulting in a downhole explosion as a result of the heat of polymerization. Also, using these conventional processes to treat long intervals of unconsolidated regions is not practical due to the difficulty in determining if the entire interval has been successfully treated with both the resin and the external catalyst.
In addition to the unconsolidated formation sands often found in subterranean formations, particulate materials are often introduced into subterranean zones in conjunction with conductivity enhancing operations and sand control operations. Conductivity enhancing and sand control operations may be performed as individual treatments, or may be combined where desired.
Therefore, it is desirable to develop a treatment method and composition to improve or maintain the rate of hydrocarbon flow and increase the overall amount of hydrocarbon flow as well as reduce fines migration, which often results in near-wellbore damage, so that the hydrocarbon flow rate and overall amount of hydrocarbon flow can be maintained at an acceptable level.